Video signal recorder and method of recording video signals

ABSTRACT

When a recording instruction is absent, a recording medium drive is not driven. Encoding of a video signal and driving of the drive are both started simultaneously when recording instruction is given. The coded data is sequentially recorded and stored in a memory. When the drive reaches a desirable rotational speed for recording, the stored data are sequentially read and recorded.

FIELD OF THE INVENTION

[0001] The present invention relates to a video signal recorder for recording video signals through coding the video signals by digital compression such as the MPEG (moving picture experts group) standard.

BACKGROUND OF THE INVENTION

[0002] Recorders employing tape, disc and other mediums have been proposed to record digitally encoded video signals.

[0003] These recorders typically require driving the recording media. These conventional recorders are thus unable to record information or data immediately after a recording instruction. In other words, several seconds are required before the driving becomes stable, when video signals are ready to be recorded. A delay for several seconds is thus inevitable from an instance when a user want to record video signals.

[0004] A method for reducing this delay has been proposed, namely, to keep driving the medium during a “pause” period. When a disc is employed as a recording medium, the disc is kept rotating during a pause period, and when a tape is employed, a cylinder is kept rotating during the pause period. In these cases, electric power is consumed although the recorder does not record anything. This can be a serious problem, for example, to a battery-driven camcorder.

SUMMARY OF THE INVENTION

[0005] A video signal recorder of the present invention comprises the following elements:

[0006] (a) coding means for encoding video signals,

[0007] (b) memory means for storing the coded data,

[0008] (c) record means for recording the coded data in a recording medium,

[0009] (d) drive means for driving the recording medium,

[0010] (e) control means for controlling all the above means or one of the above means.

[0011] The control means does not drive the drive means when a record instruction is not given. When a record instruction is given, substantially at the same time, the control means starts coding with the coding means. The control means also sequentially stores data coded in a coding circuit into a semiconductor memory. When the drive reaches to a predetermined rotational speed, the controller reads out the data stored in the memory, and then converts the data into record signals in a recording circuit. Finally, the controller records the signals in the record medium.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a block diagram of an exemplary embodiment of the present invention.

[0013]FIG. 2 is a timing chart illustrating an operation of an exemplary embodiment of the present invention.

[0014]FIG. 3 is a timing chart depicting operation of a prior art device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] An exemplary embodiment of the present invention is described by referring to FIGS. 1 through 3.

[0016]FIG. 1 is a block diagram depicting an exemplary embodiment of the present invention. An image pick up section 1 outputs video signals, which are digitally encoded in a coding circuit 2. There are two coding methods; one is a fixed rate coding method in which the coding rate is fixed, another is a variable rate coding method in which the coding rate varies momentarily responsive to complexities of video signals. Both of these methods can be used. An output from an encoding circuit 2 is stored in and is read out from a memory 3, and then is converted into a recording signal in a recording circuit 4. The record signal is recorded in a recording medium mounted on a drive 5. The memory 3 temporarily stores the data supplied from the encoding circuit 2. A control circuit 6 controls these blocks.

[0017] A timing chart according to an exemplary embodiment of the present invention is compared with that of the prior art. FIG. 3 is a timing chart of the prior art. In FIG. 3, instructions from outside, operation modes of a recorder, and rotational speeds of a drive that drives a disc or the like are indicated on a horizontal axis showing a time base. A recording mode is firstly indicated. When a pause is instructed at the time T1, the drive stops. Then, a pause-release (start recording) is instructed at the time T2, and the drive starts driving. At the time T3, the record medium reaches to a predetermined speed where the medium is ready to record, then the medium starts recording at this moment.

[0018] The difference between T2 and T3 delays the start of recording, which is a problem to be solved.

[0019]FIG. 2 is a timing chart depicting operation of the present invention. The operation in FIG. 2 corresponds to that showed in FIG. 3. In FIG. 2, instructions from outside, operation modes of a recorder, rotational speeds of a driver, coding periods, stored quantity in a memory, periods of recording data are indicated on a horizontal axis showing a time base.

[0020] A recording mode is firstly indicated. When a pause is instructed at the time T1, the drive stops. Then, a pause-release (start recording) is instructed at the time T2, and the drive starts driving. At the time T3, the record medium reaches to a predetermined speed where the medium is ready to record, then the medium starts recording at this moment. So far the operation is the same as that of the prior art. However, coding is started in the encoding circuit 2 at T2, the same time when a recording instruction is given, and the coded data is stored in the memory 3. A linear increase of stored quantity in the memory between T2 and T3 indicates this situation.

[0021] Because a rate of recording is set at a higher level than a maximum rate of coding, the stored data quantity in the memory decreases step by step by a difference between the recording rate and coding rate when recording medium starts recording at T3. In due course, the recording alters to an intermittent recording. The intermittent recording operates as follows: When data quantity stored in a memory is greater than a predetermined level A1, a record medium records the data in the medium. When the data quantity is less than a predetermined level A2, the recording in the medium is stopped. Thus the data is recorded intermittently.

[0022] When a variable coding rate is employed, the rate of recording is set at a higher level than the maximum rate of the variable coding. During the intermittent recording operation, when the stored data quantity becomes stable, an average rate of coding approximates to an average rate of recording from a macro view of point.

[0023] A period of recording data starts at T2 when the record instruction is given as shown in FIG. 2. In other words, after the instruction, video signals are coded and recorded without delay, and no power is consumed during the pause period.

[0024] There are some prior art devices that keep driving a recording medium even during the pause period, thereby reducing a delay. However, these prior art devices also keep consuming electric power due to driving, which still leaves a problem. Thus the present invention has a great advantage with regards to power savings.

[0025] In this exemplary embodiment, the encoding in the coding circuit 2 and the storing in the memory 3 simultaneously start with the record start instruction. However, the coding circuit 2 and memory 3 can be operated during the pause period. Then, a video signal picked up before a storing instruction is given can be also recorded. To record such a video signal, however, it is desirable that a co-relation between the time until a rotational speed reaches to a predetermined speed from starting and the capacity of the memory 3 be set appropriately.

[0026] The recording medium used in this embodiment can be an optical disc, magneto-optical disc, magnetic disc, or magnetic tape. Whichever of these media is used, they are within the scope of the present invention. When a disc is used, the disc halts or rotates at a predetermined speed. When a tape is used, a cylinder on which a head is mounted halts or rotates at a predetermined speed. A camcorder was referred to previously. However, the present invention is not limited to this product but also relates to a system receiving video signals from outside and having no internal image pick up section. 

What is claimed is:
 1. A video signal recorder comprising: (a) encoding means for coding a video signal; (b) memory means for storing data coded by said coding means; (c) recording means for converting the coded data into a signal to be recorded in a record medium; (d) drive means for driving the record medium, (e) control means for i) refraining from signaling said drive means to drive absent a record instruction, and ii) signalling said drive means to drive responsive to said record instruction and for recording said signal to be recorded in the record medium responsive to the record medium reaching a predetermined rotational speed for recording, wherein said signal is derived from said data stored in said memory means.
 2. The controller as defined in claim 1 , wherein said control means signals said encoding means to code the video signal substantially at the same time said record instruction is given.
 3. The video signal recorder as defined in claim 1 , wherein the video signals are produced from an image pick up device.
 4. The video signal recorder as defined in claim 1 , wherein said encoding means employs a variable coding rate method that increases data quantity and decreases data quantity responsive to video signal complexity increase and video signal complexity decrease, respectively.
 5. The video signal recorder as defined in claim 1 , wherein the record medium is one of an optical disc, magnetic disc, optical magnetic disc and magnetic tape.
 6. The video signal recorder as defined in claim 1 , in which said record instruction is absent in a pause period in which recording is halted between two record periods, said recorder remaining operating during said pause period.
 7. The video signal recorder as defined in claim 1 , wherein the record signal is recorded into the record medium when a quantity of said data stored in the memory means is greater than a predetermined amount A1, and the recording into the medium is halted when the quantity of said data stored in the memory is less than a predetermined amount A2,
 8. A video signal recorder comprising: (a) encoding means for coding a video signal; (b) memory means for storing data coded by said coding means; (c) recording means for converting the coded data into a signal to be recorded in a record medium; (d) drive means for driving the record medium, (e) control means for coding the video signal through a variable coding rate that increases data quantity responsive to a video signal complexity increase and decreases data quantity responsive to video signal complexity decrease and wherein the record signal is recorded into the record medium when a quantity of data stored in the memory means is greater than a predetermined amount A1, and the recording into the medium is halted when the quantity of data stored in the memory is less than a predetermined amount A2, and wherein the control means a) refrains from signaling said drive means to drive absent a record instruction and b) signalling said drive means to drive responsive to said record instruction and for recording said signal to be recorded in the record medium responsive to the record medium reaching a predetermined rotational speed for recording, wherein said signal is derived from said data stored in said memory means.
 9. The controller as defined in claim 8 , wherein said control means signals said coding means to encode the video signal substantially at the same time said record instruction is given.
 10. A method of recording video signals comprising the steps of: (a) encoding a video signal to generate coded data; (b) storing said coded data; (c) recording a recording signal derived from said coded data in a record medium; d) preventing driving of the recording medium when a record instruction is unavailable, e) driving the record medium substantially at the same time, said recording instruction is available, and, after the recording medium reaches a predetermined rotational speed for recording, recording said signal in the record medium.
 11. The method of recording video signals as defined in claim 10 , wherein encoding the video signal starts substantially at the same time said recording instruction is given.
 12. The method of recording video signals as defined in claim 10 , wherein data quantity of encoding is increased responsive to video signal complexity increase, and data quantity of encoding is decreased responsive to video signal complexity decrease.
 13. The method of recording video signals as defined in claim 10 , wherein said recording instruction is absent in a pause period, in which recording is halted, between two recording periods.
 14. The method of recording video signals as defined in claim 10 further comprising the step of: recording said recording signal into the recording medium when a quantity of said data stored in the memory is greater than a predetermined amount A1, and halting recording of said recording signal into the record medium when the quantity of said data stored in the memory is less than a predetermined amount A2.
 15. A method of recording video signals comprising the steps of: (a) encoding a video signal to generate coded data; (b) storing said coded data; (c) recording a recording signal derived from said coded data in a record medium; (d) driving the record medium, increasing data quantity of encoding responsive to video signal complexity increasing and decreasing data quantity of encoding responsive to video signal complexity decreasing, wherein the recording signal is recorded into the record medium when a quantity of said data stored in the memory is greater than a predetermined amount A1, and recording of the recording signal into the record medium is halted when the quantity of said data stored in the memory is less than a predetermined amount A2, and preventing driving of the recording medium when a recording instruction is unavailable, driving the record medium substantially at the same time, said recording instruction is available, and, after the record medium reaches a predetermined rotational speed for recording, recording said signal in the record medium.
 16. The method of recording video signals as defined in claim 15 , wherein said encoding the video signal starts substantially at the same time said recording instruction is given. 